# NAD+: The Cell's Redox Coenzyme, Read Through the Research > NAD+ is the central redox coenzyme every cell uses to make energy. A research digest of the oral-precursor and IV/injectable NAD+ literature, cited to source. A console reading of what the published studies measured: oral NMN and NR reliably raise blood NAD+, infused NAD+ clears the plasma in hours, and every figure on this page carries its citation. ## The short version NAD+ (a fuel-handling helper molecule every cell uses to turn food into energy) is not a drug and is not one product on a shelf. It is a coenzyme — a helper molecule an enzyme needs to do its job — that your body makes and that drops in your tissues as you age. Most things sold as "NAD+" are actually **precursors** (building blocks the body converts into NAD+ — NMN and NR are the common ones), because NAD+ itself is large and poorly absorbed when swallowed. This page reads what the studies measured, route by route, and cites each number. ## What NAD+ is, in one console readout NAD+ stands for nicotinamide adenine dinucleotide. It is the cell's central redox carrier — "redox" being the electron-shuttling chemistry that releases energy — cycling between an oxidized form (NAD+) and a reduced form (NADH) as it moves electrons through glycolysis, the TCA cycle, and the mitochondrial electron transport chain to make ATP [5]. It is also a *consumed* substrate: the enzymes sirtuins (a family of cellular-maintenance enzymes that cannot work without NAD+), PARPs (DNA-repair enzymes), and CD38 all spend NAD+ as they run [5]. The molecule is a dinucleotide, not a peptide: a nicotinamide ring joined to an adenine nucleotide through two bridging phosphates, molecular formula C21H27N7O14P2, molecular weight 663.43 Da, CAS 53-84-9. Tissue NAD+ falls with age, and one driver is the NAD+-consuming ectoenzyme CD38, which rises with age and inflammation [2][5]. That decline is the entire rationale behind the supplement market — and behind this digest reading what the [NAD+ and precursor studies](/research) actually found. If you want the one-paragraph version of [what NAD+ is](/) before going deeper, the short version sits at the top of this page; the [common NAD+ questions](/faq) cover the rest. ## NAD+ as a Supplement: Why Most Products Are Precursors An NAD supplement is, in practice, almost never NAD+ itself. NAD+ is a large, charged molecule that cells do not freely take up intact, so swallowing NAD+ is widely considered an inefficient way to raise it. The rational oral approach is a **precursor** the body converts to NAD+ inside the cell — chiefly NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside), both vitamin-B3-family molecules, plus plain niacin and nicotinamide. These are sold as **dietary supplements**, not approved drugs. The precursor data is the strong part of the human record. In a randomized trial, NR at 100, 300, and 1000 mg/day for 8 weeks raised whole-blood NAD+ by 22%, 51%, and 142% respectively, with no significant adverse-event difference from placebo at any dose [4]. NMN at 300, 600, and 900 mg/day for 60 days likewise raised blood NAD+ at days 30 and 60 across all groups versus placebo (p ≤ 0.001) in a multicenter double-blind trial [3]. The two leading oral options are compared as [NMN vs NR precursors](/research) on the research page. The honest caveat: raising blood NAD+ is well demonstrated; translating that to hard clinical outcomes in humans remains preliminary, a point a 2025 *Nature Metabolism* review made directly [14]. One marketplace note belongs here. The regulatory status of NMN is contested: the FDA has taken the position that NMN is excluded from the dietary-supplement definition because it was authorized for investigation as a drug. That is a marketplace dispute over a category, not a finding that NMN is banned or unsafe [14]. None of NAD+, NMN, NR, or nicotinamide is prohibited by WADA. ## Two routes the search demand conflates: oral, IV, and injectable Search interest treats "NAD+," "NAD injection," and "NAD IV therapy" as one thing. The studies do not. The route changes the evidence and the pharmacokinetics, so this digest keeps them on separate channels. **Oral precursors** carry the bulk of the controlled human data: capsules or powder of NMN, NR, or nicotinamide, absorbed over days, raising whole-blood NAD+ that stays elevated through 8-to-12-week dosing [3][4]. **IV NAD+** is a compounded, unapproved wellness therapy with the weakest controlled evidence; a pharmacokinetic pilot infusing 750 mg over 6 hours found plasma NAD+ undetectable for roughly the first 2 hours, with extensive extracellular metabolism — infused NAD+ is rapidly cleared [6]. **Injectable NAD+** (subcutaneous or intramuscular, compounded) has minimal peer-reviewed pharmacokinetic data. The injectable lens is covered in depth on [NAD injection research](/nad-injection) and [NAD IV therapy](/nad-iv-therapy). ## What does NAD do for the body? NAD+ is the cell's central redox carrier that shuttles electrons to make ATP, and a consumed substrate for sirtuins, PARPs, and CD38 — enzymes that govern DNA repair, gene regulation, and inflammation [5]. Tissue NAD+ declines with age, partly because CD38 activity rises [2]. It is foundational cellular machinery, present in every living cell, not an optional add-on. ## Is NAD a peptide? No. NAD+ is not a peptide. It is a dinucleotide coenzyme — a nicotinamide ring plus an adenine nucleotide joined by phosphate groups, molecular formula C21H27N7O14P2, molecular weight 663.43 Da. Peptides are short chains of amino acids; NAD+ shares none of that structure. ## What does NAD stand for? NAD stands for nicotinamide adenine dinucleotide. Its oxidized form is written NAD+ and its reduced form NADH; the two interconvert as the coenzyme shuttles electrons during metabolism [5]. It was historically also called Coenzyme I or DPN (diphosphopyridine nucleotide). ## What does NAD mean in medical terms? In biochemistry, NAD means nicotinamide adenine dinucleotide, a coenzyme essential for hundreds of oxidoreductase reactions and for sirtuin, PARP, and CD38 signaling [5]. It is endogenous — synthesized in every cell from tryptophan, nicotinic acid, and the salvage pathway — not a prescribed medicine. ## Is NAD just vitamin B3? NAD+ is not vitamin B3 itself, but it is built from B3-family precursors — niacin, nicotinamide, and nicotinamide riboside. NAD+ is the dinucleotide coenzyme those vitamins are converted into inside cells through the salvage and Preiss-Handler pathways [5]. The vitamins are the input; NAD+ is the product. ## Is taking NAD orally effective? Oral NAD+ itself is poorly taken up by cells intact, so most experts consider oral **precursors** (NMN, NR) the rational approach. Precursor trials reliably raise blood NAD+ — NR by up to 142% at 1000 mg/day [4] — while plain oral "NAD+" capsules are widely considered largely ineffective for raising the coenzyme. ## What is NAD supplement used for? NAD supplements — mostly precursors like NMN and NR sold as dietary supplements — are marketed and studied for raising the blood NAD+ that declines with age [3][4]. Research has measured effects on muscle insulin sensitivity and physical performance [1][3], but human efficacy for hard clinical endpoints remains preliminary [14]. This is description of studies, not a use recommendation. --- A chrome console reading of the NAD+ record — the coenzyme, its oral precursors, and the injectable studies logged route by route and cited to source, with oral NAD+'s poor absorption and IV NAD+'s rapid clearance flagged in plain sight; no clinic behind the readout and nothing here prescribed, compounded, or sold.